Machining, e.g., milling operations are often accompanied by vibration that occurs during the interaction of a cutting tool with a workpiece. This vibration is often referred to as self-excited vibration, regeneration vibration, or chatter. Chatter is an unstable condition occurring, primarily, in high-speed machining operations and may result in undesirable surface defects requiring substantial post-processing to eliminate. In extreme cases, the machined surface may be damaged beyond repair, rendering the workpiece unusable. Due to its regenerative nature, chatter may become sufficiently violent to damage the cutter and even the machine tool itself.
One method commonly employed to mitigate regenerative vibration or chatter includes reducing the depth of cut. However, this technique is associated with a reduction in material-removal rate and decreased productivity. Adjusting the rotational speed of the spindle to match the “cutting” frequency (related to the number of times the teeth of the cutter contact the workpiece in a given time period), or its harmonics, with the natural frequency of the system is another option available in controlling chatter. However, the spindle speed optimal for a particular cutting tool, tool holder, and spindle combination may be unavailable on a given machine tool, may be unsuitable for the cutter, or may result in lower production rates. Another approach used in reducing chatter is adjusting the length or “stick-out” of the cutting tool to change the system's natural frequency. However, this method has limited effect, since the range of “stick-out” adjustment is restricted. Specialized cutting tools have also been developed to abate chatter in various machining applications, but the higher cost of such tools has been a disadvantage.